Hi, I downloaded the code from your site , and I debugged the source code of UltraWebGrid component( Infragistics35.WebUI.UltraWebGrid2.v8.3  HotFix 2021)

The exception was raised in the line  1532 of the class

Infragistics.WebUI.UltraWebGrid.DBBinding

if (!(datasource is DataView) && currentBand.Index == 0)

because the currentBand is null

This happened when the grid tried to create the childs rows of the first row.

I  tried to fix the problem by my self and I was discovered that your component cannot clean the bands and  other structures after that assign a null value to datasource and raise a databind metohod.  And not regenerate  the new bands after assign the new datasource.  

This was happened when I used collections with subcollections members.

The solutions was very easy.  With the same code, that I sent before, I called a bands clear method of DisplayLayout of the grid.

  If Me.IsPostBack Then
                Try
                    Me.UltraWebGrid1.DataSource = Nothing
                    Me.UltraWebGrid1.DataBind()
                    Me.UltraWebGrid1.DisplayLayout.Bands.Clear()
                    Me.UltraWebGrid1.DataSource = Session("InvoiceData")
                    Me.UltraWebGrid1.DataBind()
                Catch ex As Exception
                    Me.lblMessage.Text = ex.Message
                End Try

            End If

With this  code my program works very well for the moment.

Thanks for all.

Javier.
solisaj@bccr.fi.cr
MCP,MCTS,MCPD

Thanks for the update, and for mentioning your case number.  We're still looking into this issue, based on what progress I see on the case.